The total invoice should be of $3450. Though this defect was easy to find, as credit amount and discount amount is not too much. Last year my company was to get merged with one similar company , but the problem was coming on the side of reconciliation of the account. Inspite of our best services, we were not able to find the wrong figure. We have taken the services of Investmentbank https://investmentbank.com/valuations/mergers/. They provided a very good service in this regard.